OBJECTIVE: To investigate whether body mass index (BMI) is a prognostic factor for biochemical recurrence (BCR) in Dutch men after radical prostatectomy (RP), as although epidemiological studies of obesity in relation to prostate cancer have provided conflicting results, recent studies from the USA suggest that a higher BMI is a risk factor for progression of prostate cancer. PATIENTS AND METHODS: Of the 1417 patients with prostate cancer who had RP at two University hospitals, 1302 were included in the present study. BMI (kg/m(2)) classes were defined as normal (&lt;25), overweight (25-30) and obese (&gt; or =30). The median follow-up was 59 months and clinical data were obtained retrospectively from charts. BCR was defined as two consecutive prostate-specific antigen (PSA) levels of &gt;0.1 ng/mL. RESULTS: In all, 600 patients were classified as having normal weight (43.9%), 665 as overweight (48.6%) and 103 as obese (7.5%). Overall, 297 patients developed BCR after RP; the 10-year risk (95% confidence interval) of BCR was 31.9 (26.6-37.2)%, 30.5 (25.8-35.2)% and 23.9 (14.9-32.9)% for patients in the three categories, respectively (P = 0.836). Multivariable proportional hazard regression analyses of BMI and established prognostic factors for BCR did not change these results. CONCLUSION: BMI appeared to have no prognostic value for BCR in Dutch patients with clinically localized prostate cancer and treated with RP.